HV739DB1
HV739 ±100V 3.0A Ultrasound Pulser Demo Board
Introduction
Designing a Pulser with the HV739
The HV739 is a monolithic single channel, high-speed, high
voltage, ultrasound transmitter pulser. This integrated, high
performance circuit is in a single, 5x5mm, 32-lead QFN
package.
This demo board data sheet describes how to use the
HV739DB1 to generate the basic high voltage pulse waveform as an ultrasound transmitting pulser.
The HV739 can deliver up to a ±3.0A source and sink current
to a capacitive transducer. It is designed for the ultrasound
material inspection NDT and medical ultrasound imaging
applications. It can also be used as a high voltage driver
for other piezoelectric or capacitive MEMS transducers, or
for ATE systems and pulse signal generators as a signal
source.
HV739’s circuitry consists of controller logic circuits, level
translators, gate driving buffers and a high current and high
voltage MOSFET output stage. The output stages of each
channel are designed to provide peak output currents over
±3.0A for pulsing, with up to ±100 volt swings. Two floating 12VDC power supplies referenced to VPP and VNN supply
the P- and N-type power FET gate drivers. The upper limit
frequency of the pulser waveform is 35MHz depending on
the load capacitance. The HV739 can also be used as a
damping circuit to generate fast return-to-zero waveforms
by working with another HV739 as a pulsing circuit. It also
has built-in under-voltage and over-temperature protection
functions.
The HV739 circuit uses the DC coupling method in all level
translators. There are no external coupling capacitors needed. The VPP and VNN rail voltages can be changed rather
quickly, compared to a high voltage capacitor gate-coupled
driving pulser. This direct coupling topology of the gate drivers not only saves two high voltage capacitors per channel,
but also makes the PCB layout easier.
The input stage of the HV739 has high-speed level translators that are able to operate with logic signals of 1.8 to 5.0V
volts and are optimized at 3.3 to 5.0V. In this demo board,
the control logic signals are connected to a high-speed ribbon cable connector. The control signal logic-high voltage
should be the same as the VCC voltage of the demo board,
and the logic-low should be reference to GND.
The HV739DB1 output waveforms can be displayed using
an oscilloscope directly by connecting the scope probe to
the test point HVOUT and GND. The soldering jumper can select whether or not to connect the on-board equivalent-load,
a 330pF, 200V capacitor, parallel with a 2.5kΩ, 1W resistor.
A coaxial cable can be used to connect the user’s transducer
to easily drive and evaluate the HV739 transmitter pulser.
Application Circuit
+3.3V
+12V
VLL
+100V (VPP-12V) 0 to +100V
VSUB
VDD
VPP
VPF
VCC
OTP
RGND
EN
Logic
Control
Level
Translator
PIN1
P-Driver
TXP
NIN1
HVOUT
HV739
GREF
Level
Translator
TXN
N-Driver
GND
RGND
VNF
VSS
VNN
GND
(VNN+ 12V)
0 to -100V
HV739DB1
The PCB Layout Techniques
Testing the Integrated Pulser
The large thermal pad at the bottom of the HV739 package
is connected to the VSUB pins to ensure that it always has
the highest potential of the chip, in any condition. VSUB is the
connection of the IC’s substrate. PCB designers need to pay
attention to the connecting traces as the output high-voltage
and high-speed traces. In particular, low capacitance to the
ground plane and more trace spacing need to be applied in
this situation.
The HV739 pulser demo board should be powered up with
multiple lab DC power supplies with current limiting functions.
The following power supply voltages and current limits have
been used in the testing: VPP= 0 to +100V 10mA, VNN= 0
to -100V 10mA, VDD= +12V 20mA, (VPP-VPF) = +12V 20mA,
(VNF-VNN) = +12V 20mA. VCC= +3.3V 5.0mA for HV739 VLL,
not including the user’s logic circuits.
The power-up or down sequences of the voltage supply
ensure that the HV739 chip substrate VSUB is always at the
highest potential of all the voltages supplied to the IC.
High-speed PCB trace design practices that are compatible
with about 50 to 100MHz operating speeds are used for the
demo board PCB layout. The internal circuitry of the HV739
can operate at quite a high frequency, with the primary speed
limitation being load capacitance. Because of this high speed
and the high transient currents that result when driving
capacitive loads, the supply voltage bypass capacitors and
the driver to the FET’s gate-coupling capacitors should be
as close to the pins as possible. The VSS pin pads should
have low inductance feed-through connections that are
connected directly to a solid ground plane. The VDD, VPP, VPF,
VNF and VNN supplies can draw fast transient currents of up
to ±3.0A, so they should be provided with a low-impedance
bypass capacitor at the chip’s pins. A ceramic capacitor of
up to 0.22 to 1.0µF may be used. Minimize the trace length
to the ground plane, and insert a ferrite bead in the power
supply lead to the capacitor to prevent resonance in the
power supply lines. For applications that are sensitive to
jitter and noise, and for using multiple HV739 ICs, insert
another ferrite bead between VDD and decouple each chip
supply separately.
The (VPP–VPF) and (VNF–VNN) are the two floating power
supplies. They are only 12V, but floating with VPP and VNN.
The floating voltages can be trimmed within the range of
+8.0~+12V to adjust the rising and falling time of the output
pulses for the best HD2. Do not exceed the maximum voltage
of +12V. The VPP and VNN are the positive and negative high
voltages. They can be varied from 0 to +/-100V maximum.
Note when the VPP= VNN= 0, the VPF and VNF in respect to the
ground voltage is –12V and +12V.
The on-board dummy load 330pF//2.5kΩ should be connected
to the high voltage pulser output through the solder jumper
when using an oscilloscope’s high impedance probe to meet
the typical loading condition. To evaluate different loading
conditions, one may change the values of RC within the
current and power limit of the device.
In order to drive the user’s piezo transducers with a cable,
one should match the output load impendence properly to
avoid cable and transducer reflections. A 50Ω coaxial cable
is recommended. The coaxial cable end should be soldered
to the HVOUT and GND directly with very short leads. If a
user’s load is being used, the on-board dummy load should
be disconnected by cutting the small shorting copper trace
in between the zero ohm resistors R7, R8, R9 or R10 pads.
They are shorted by factory default.
Pay particular attention to minimizing trace lengths and using
sufficient trace width to reduce inductance. Surface mount
components are highly recommended. Since the output
impedance of HV739’s high voltage power stages is very
low, in some cases it may be desirable to add a small value
resistor in series with the output to obtain better waveform
integrity at the load terminals. This will, of course, reduce the
output voltage slew rate at the terminals of a capacitive load.
Be aware of the parasitic coupling from the outputs to the
input signal terminals of HV739. This feedback may cause
oscillations or spurious waveform shapes on the edges of
signal transitions. Since the input operates with signals
down to 1.8V, even small coupling voltages may cause
problems. Use of a solid ground plane and good power and
signal layout practices will prevent this problem. Also ensure
that the circulating ground return current from a capacitive
load cannot react with common inductance to create noise
voltages in the input logic circuitry.
All the on-board test points are designed to work with the
high impedance probe of the oscilloscope. Some probes
may have limited input voltage. When using the probe
on these high voltage test-points, make sure that VPP/VNN
voltages do not exceed the probe limit. Using the high
impendence oscilloscope probe for the on-board test points,
it is important to have short ground leads to the circuit board
ground plane.
Precautions need to be applied to not overlap the logic-high
time periods of the control signals. Otherwise, permanent
damage to the device may occur when cross-conduction
or shoot-through currents exceed the device’s maximum
limits.
2
HV739DB1
HV739DB1 Schematic
VCC
VDD
VSUB
VPF
VPP
TP1
TP2
TP12
TP3
C2
D1
DFLT13A
2
1
C3
0.22
C5
0.22
1.0
4
29
28
27
VP P
VP P
VP P
TXP
TXP
TXP
OTP
EN
U1
HV739
TP7
5
30
VS UB
VS UB
VS UB
VS UB
VLL
VP F
1
7
EN
NIN
PIN
OTP
2
4
6
8
J3
TP5
PIN
11
TP13
C7
3
2
1
D3
DFLT13A
VNF
VNN
VPP
VNN
VNF
VPF
VPP
2
D7
1
D6
R4
1
R5
10
R6
10
R7
10
R8
10
J2 HEADER 8
HV739DB1 PCB
3
TP11
R9
10
C8
1u 100V
VSUB
VNN
B1 10 0-1 3
2
VDD
D5
2
4
3
VPP
VNN
D9B
B1 10 0-1 3
D9A
BAT54DW-7
D4
6
D8B
1
3
4
6
1
VCC
BAT54DW-7
D8A
VPP
1
VSUB
B1 10 0-1 3
VSUB
1
VPF
2
VNF
B1 10 0-1 3
VCC
1
VDD
VDD
1
2
3
4
5
6
7
8
2
R13
50
VCC
C6
330p 200V
TP9
1.0
1
J5
TX
R2
0
VNN
VNN
VNN
GREF
8
3
12
13
14
R14
50
R11
50
17
18
19
NIN
VNF
2
TP10
TP6
2
TXN
TXN
TXN
VS S
3
1
J4
D2
BAV99
1
3
TP8
6
22
23
24
R10
10
+100V>VSUB>VPP
VCC = +3.3V
VDD = +12V
(VPP - VPF) = +12V
(VNF - VNN) = +12V
VPP = 0 to +100V
VNN = 0 to -100V
3
1
3
5
7
TP4
1
2
VCC
2
VDD
R1
1K
R12
200
9
16
25
32
1u 100V
HEADER 4 X2
C1
1u 100V
C4
R3
2.55K 1W
J1
HVOUT
HV739DB1
Board Voltage Supply Power-Up Sequence
1
VCC
+1.2 to 5.0V positive logic supply voltage for HV739 VLL and user logic circuit.
2
VDD
+12V positive drive supply voltage
3
VPF and VNF
4
VSUB
5
VPP / VNN
6
Logic Active
Floating supply voltages, (VPP- VPF)= +12V and (VNF- VNN) = +12V
+100V>VSUB/VPP positive bias voltages
0 to +/-100V positive and negative high voltages
Any logic control active high signals
Note: The Power-down sequence should be revising as to the power-up sequence above
Connector and Test Pin Description
Logic Control Signal Input Connector
1
VCC
Logic-high reference voltage input, VLL, +1.2 to 5.0V, normally from control circuit.
2
EN
3
GND
Logic signal ground, 0V (2).
Pulser output enable logic signal input, active high.
4
NIN1
Logic signal input for CH1 negative pulse output, active high. (1)
5
GND
Logic signal ground, 0V.
6
PIN1
Logic signal input for CH1 positive pulse output, active high. (1)
7
GND
Logic signal ground, 0V.
8
OTP
Open drain output of over-temperature protection logic signal, active low.
Power Supply Connector
Logic-high reference voltage supply, +1.2 to 5.0V current limit 5.0mA (for VLL only).
1
VCC
2
GND
3
VDD
+12V positive driver voltage supply with current limit to 10mA.
4
VNN
0 to -100V negative high voltage supply with current limit to 5.0mA
5
VNF
Floating voltage supply (VNF-VNN) = +12V with current limit to 10mA. (3)
6
VPF
Floating voltage supply (VPP-VPF) = +12V with current limit to 10mA. (3)
7
VPP
0 to +100V positive high voltage supply with current limit to 2.0mA
8
VSUB
Chip substrate bias voltage, must be (+100V>VSUB/VPP) with limit to 5.0mA
Low voltage power supply ground, 0V
Note:
(1). Overlap control signals logic-high periods of PIN and NIN may cause the device permanent damage.
(2). Due to the speed of logic control signal, every GND wire in the ribbon cable must connect to signal source ground.
(3). (VPP-VPF) and (VNF-VNN) floating voltage can be trimmed from +8V to +12V for tr/tf time matching. Do not exceed the maximum +12V.
4
HV739DB1
HV739DB1 Waveforms
Figure 1: NIN, PIN and output waveform of 5.0MHz, VLL= 3.3V, VDD= +12V, (VPP-VPF) = +12V, (VNF-VNN) = +12V,
VPP/VNN= +/-48V, VSUB= +100V with load of 330pF//2.5K.
Figure 2: NIN, PIN and output waveform of 10MHz, VLL= 3.3V, VDD= +12V, (VPP-VPF) = +12V, (VNF-VNN)= +12V,
VPP/VNN= +/-48V, VSUB= +100V with load of 330pF//2.5K.
5
HV739DB1
HV739DB1 Waveforms (cont.)
Figure 3: NIN, PIN and output waveform of 20MHz, VLL= 3.3V, VDD= +12V, (VPP-VPF)= +12V, (VNF-VNN)= +12V,
VPP/VNN= +/-48V, VSUB= +100V with load of 330pF//2.5K.
Figure 4: Input to output propagation delay on falling edge is 16.4ns and the tr/tf time are about 10ns/12ns.
VLL= 3.3V, VDD= +12V, (VPP-VPF)= +12V, (VNF-VNN)= +12V, VPP/VNN= +/-48V, VSUB= +100V with load of 330pF//2.5K.
6
HV739DB1
HV739DB1 Waveforms (cont.)
Figure 5: Input to output propagation delay on rising edge is 18ns and the tr/tf time are about 10ns/12ns.
VLL= 3.3V, VDD= +12V, (VPP-VPF)= +12V, (VNF-VNN)= +12V, VPP/VNN= +/-48V, VSUB= +100V with load of 330pF//2.5K.
Figure 6: Input to output waveforms of the tr/tf time are about 13ns/13ns at VLL= 3.3V, VDD= +8.5V, (VPP-VPF)= +8.5V,
(VNF-VNN)= +8.5V, VPP/VNN= +/-48V, VSUB= +100V with load of 330pF//2.5K.
7
HV739DB1
HV739DB1 Waveforms (cont.)
Figure 7: Input to output waveforms of the tr/tf time are about 10ns/12.3ns at VLL= 3.3V, VDD= +12V, (VPP-VPF)= +12V,
(VNF-VNN)= +12V, VPP/VNN= +/-48V, VSUB= +100V with load of 330pF//2.5K.
NR072007
8